Analysis:

The concept of physics has undergone profound changes in the 20th century. People have stepped from "classic" or "Newton" physics to "modern" physics, thus promoting the development of physics. From this point of view, physics in the19th century seems to be a "survival" stage between "classic" and "modern". /kloc-how far has physics developed in the 0/9th century? How does it relate to the emergence and development of "modern" physics?

The Development of Physics Concepts in the19th Century-Energy, Force and Matter (by Peter Michael Harman, translated by Gong, published by Fudan University Press) is one of the series of Cambridge History of Science. The author Professor Hahn briefly explained the theoretical framework of physics in the19th century, focusing on the process that physicists at that time tried their best to establish their own theories on the basis of mechanism. Although as far as my current knowledge of physics is concerned, my understanding of the whole book can only be superficial, I think that in the critical period of perfecting and gestating the two pillars of physics in the19th century, when we worship them devoutly, study and study their theoretical knowledge, and delve into a large number of exercises, we not only need a common sense understanding of physics, but at least for me, we feel that it is beneficial.

The whole book can be said to be a chronicle of physics in19th century. Starting with how to further expand the scope of physics in the first half of the19th century, this book focuses on several conceptual problems in the19th century-the appearance of energy physics and thermodynamics, the theories of luminous ether and electromagnetic ether, the concepts of field theory, molecular physics and statistical thermodynamics, and the dominant position of mechanical interpretation program.

The book is full of dull theoretical explanations, many of which involve physical knowledge that we haven't touched yet. Such as ether, molecular physics and so on, but there is always an idea that keeps me reading this book. Because what really attracts me is not only these theories and formulas, but also the thinking traces of these physicists during the transition from "classical" physics to "modern" physics. I am eager to know: what kind of height did the concept of physics develop in the19th century, and what was the core problem of physics in the whole19th century?

/kloc-physics in the 0/9th century-the perfect combination of physics and mathematics

At first, when I read this book, I was often surprised to find out why there are so many famous mathematicians' names in this physics reading book-these names are frequent visitors in the advanced mathematics book we are studying-Laplace, Fourier, Lagrange ... They have developed a series of mathematical formulas, which takes us a long time to digest and understand, which is very rare. I didn't expect them to "get involved" in the field of physics. With the deepening of the content, my understanding is gradually full: in the19th century, the meaning of the term "physics" has changed greatly. Although this term is sometimes used to refer to the natural science in the traditional sense, in the early19th century, "physics" has been used to refer to the modern science that uses mathematical methods and experimental methods to study mechanics, electricity and optics. At that time, the physical research methods mainly used quantitative description, with the general goal of seeking mathematical laws, and the establishment of the unified principle of the law of conservation of energy and the mechanical interpretation program as the pillars of physical theory.

[i] In the physical theory of19th century, mechanical phenomena were analyzed and studied on the basis of mathematics. It can be said that the mathematical treatment of physical phenomena has reached its peak in mechanical research. Mainly reflected in the following four aspects of progress. They laid a reliable foundation for the establishment of unified physics:

1.P. S De Laplace and his followers established a general mathematical theory about the force between particles, which is applicable to mechanics, thermal and optical phenomena as well. Although this theory was abandoned with the latest progress of heat and optics in the period of 18 15- 1825, Laplace's mathematization and formulation had a far-reaching impact on the unified physical world outlook and even on the development of physical theory in the future.

2. 1822 Publication of Joseph Fourier's Mathematical Theory on Heat 1 Apply the mathematical analysis method originally only applicable to mechanical problems to the study of heat. Fourier's work runs in this traditional conceptual difference, and when emphasizing the difference between mathematical expression and physical expression, it has a far-reaching and extensive impact on the establishment of unified physics. It is under this influence that William Tang Musun got inspiration from the mathematical similarity between his thermal theory and electrostatic theory in the 1940s from 65438 to 2009. On the one hand, he studied the mathematical similarity and physical similarity between the laws of thermodynamics and electricity, on the other hand, he explored the mathematical similarity between particle mechanics, fluid mechanics and elasticity. Tang Musun deepened people's understanding of the unity of physical phenomena through this physical comparison method and the conceptual connection method between different phenomena reflected in the same mathematical form.

3. A.J. Fresnel's theory about the fluctuation of light assumes that light propagates through the vibration of mechanical ether, so optics has been included in the category of mechanical natural view. About 65438+1930s, the wave theory of light has been generally accepted. Physicists try to find the logical theory of optical mechanics and explore various physical and mathematical theories. The mechanistic theory of optical ether provides a typical universal example for mechanical explanation.

4.65438+In the 1940s, the law of conservation of energy was established, which strengthened the unity of physics and made heat, light, electricity, magnetism and other phenomena integrated into the framework of mechanical principles. Herman Helmholtz expressed these phenomena as different forms of energy in a very creative paper published in 1847, thus explaining the relationship among mechanics, heat, optics, electricity and magnetism. He also emphasized that the concept of energy is another expression of mechanical view of nature, and the law of conservation of energy he established is also a theorem of mathematics and mechanics.

Although many physicists have failed in trying to solve some problems by mathematical methods, on the whole, the development of physics in the19th century is a perfect combination of physics and mathematics. It is the perfect combination of mathematics and physics that makes the subject scope and content of "physics" extremely wonderful. As a complete discipline, physics has not only been further supplemented and improved in extension and connotation, but also reached a new stage of accurate concept and logical unity.

/kloc-the decline of physics-mechanics worldview in the 0/9th century

Looking back at physics in the19th century, around 1850, the most important foundation of physics at that time was clear: all physical phenomena can be explained by a unified framework, that is, taking mechanical explanation as the starting point of the principle, simulating physical phenomena through mathematical description, and deducing mathematical equations to describe them, and then taking the law of the universe-the law of conservation of energy as the crown. With the support of classical mechanics and the establishment of energy conservation law, people's understanding of force and energy has reached a higher level. However, when physicists try to perfect this physical system with mechanics as the main body and expect to rely on this system to explain the laws of nature, difficulties and contradictions unexpectedly appear. Everything is just as W. Tang Musun pointed out in his speech entitled "Dark clouds floating over the thermal and optical dynamics in the 1900 century": the mechanical view of nature faces two major problems, one is that it cannot explain the movement mechanism of the earth through the ether; Second, the concept of energy sharing can not put forward the construction of molecular model. Tang Musun emphasized that it was these two "dark clouds" that prevented him from putting forward a mechanical model of physical phenomena. However, because these two problems involve a wide range, physicists also have a lot of room to pay attention to the conceptual basis of the mechanical view of nature.

In fact, I think the traditional mechanical interpretation program caused various reactions among physicists in the 1980s and 1990s of 19. However, in the process of explanation, there will inevitably be some difficulties or difficulties. This seems to be the bottleneck of physics research at that time. For example, Tom Musun's ether model 3 and Boltzmann's lecture on field theory all try to explain the model of physical phenomena and do everything possible to maintain the mechanical program. Boltzmann described the structure and motion of his electromagnetic field mechanical model in detail. Tang Musun pointed out that the structure of the mechanical model of phenomena is an important criterion for easy understanding of phenomena; However, the conceptual difficulties related to mechanical models have been deeply understood. Hertz also believes in mechanical interpretation programs, emphasizing that his concept of ether is based on the model that all parts of ether are connected by mechanical structures. However, because he carefully distinguished the form of electromagnetic field from the form of mechanical model, it prompted him to have the view that electromagnetic field has no mechanical properties. In his first description of the electronic theory, he imagined the electromagnetic field as a dynamic system, but he finally gave up the form related to analytical dynamics and did the opposite, and established the ontology of electrons and electromagnetic ether within the scope of non-mechanical principles, while his electromagnetic ether theory was not based on mechanical programs. Lorenz explained the movement of the earth through the ether from his own electromagnetic nature view, which is also a way to avoid the difficulties faced by the mechanical theory of elastic ether. The debate about the mechanism of field theory is exactly the same as that about thermodynamics. Boltzmann tried his best to maintain the unshakable position of mechanical nature view. After establishing the concepts of entropy and irreversibility with the statistical principle of molecules, he explained the second law of thermodynamics with the ontology of mechanical view of nature. Planck did not completely deny the ontology of mechanism, but he tried to explain entropy with pure heat. In a word, they all want to remove the concept of atomism from the category of physical theory.

Because of the related problems such as the principle of equipartition and the structure of ether model, that is, two' dark clouds' appeared above Tang Musun's so-called mechanical view of nature, the debate about the basic framework of physics building became more and more prominent. Whether replacing the mechanical program with electromagnetism ontology, or the principle of energy balance conforms to the theory of gas motion, or in the process of seeking a purely mechanical explanation for entropy, all kinds of failures have accelerated the decline of the mechanical program. As an example of the evolution of physical theory, this extinction is deeply supported by philosophical critics of mechanical explanation.

I don't want to discuss this philosophical criticism here. At least now we know that Tang Musun's two "dark clouds" have finally dissipated, of course, not through his revision of the mechanical and physical mechanism. /kloc-in the second half of the 9th century, with the deepening of the understanding of physical explorers, the demise of mechanical programs promoted the germination of new physical systems, and also completed the transition from classical physics relying on mechanical programs to modern physics.

/kloc-physics in the 0/9th century-the link between "classic" and "modern"

Here, I just want to talk about my perceptual knowledge of the development of physics in the19th century from the perspective of a beginner in physics.

Always amazed at the magnificent palace of physics supported by "classical physics" and "modern physics"; I always thought that the leap from "classical mechanics" to "modern physics" was a flash of light from several physical geniuses-everything was like the description in Newton's epitaph: "Nature and its laws are hidden in the dark. God said, "Let Newton go." Everything is bright. "God created Newton, and it also created this apple that fell on Newton's head, so the three laws of Newton's mechanics were born-Einstein, a genius, also had an accidental flash of light, patted his head, came up with a" relative space "that was outside the" absolute space "and constructed a series of time and space views that were regarded as classics by people. As we all know, when the wheel of physics and human civilization rolled forward and went away from18th century, how great changes have taken place in the concepts, theories and concepts of physics during this100th century. In this 100 year, which is like a drop in the ocean, physical explorers have to shuttle back and forth in completely different thinking to find the fulcrum of balance. No matter how prominent the dominant position of mechanical interpretation program is, no matter how strong the actual situation of occasionally resorting to Newton's theory is, the word "Newton's" is often misunderstood when it is applied to physics in the19th century. /kloc-the concepts of physics in the 0/9th century-energy conservation, physical field theory, electromagnetic ether oscillation and luminescence theory, and the concept of entropy-can no longer be expressed by Newton. Truth seems to be fallacy, and new theories seem to wander in the dim light. Everything seems to be in a mess, with no clue. During the online discussion, some students had such a question: If one day, all theories before the development of physics must be overturned, what should we do? Our answers are all optimistic and understated "start all over again". Imagine, didn't the physical explorers at that time face a similar situation? Some unusual forms of physics, similar to Newton's view of nature, have long been regarded as truth. Who can understand the confusion and confusion? Old school or pioneer? -on the one hand, it is a traditional principle that we strive to maintain, on the other hand, it is an emerging concept that is ready to come. Who can imagine the collision and friction between these two ideas? Keep or discard? -When new ideas begin to shine, who can imagine the skeptical, critical and critical eyes that must be experienced in this process? And in order to maintain these budding ideas, who can imagine what kind of bold ideas and careful inferences are needed? ……

/kloc-the development of physics in the 0/9th century, although there is no theory that can be compared with the "three laws of mechanics" or "relativity", I think it is not an exaggeration to describe it as "a hundred flowers blossom and a hundred schools of thought contend". Because, like a baby full of vitality, it is getting rid of the false and retaining the true, summing up and perfecting the "classical mechanics" system, and at the same time, it is also preparing for a new and equally great theory; It is like a link between classical physics and modern physics, and it is an important and special stage in the development of physics.

In the 16 and 17 centuries, the intellectual victories of mechanics and astronomy left a clear impression on the history of scientific revolution, but also left a very wrong impression on the rock-solid unified world outlook of "classical" physics; In the 20th century, Einstein abandoned the concept of absolute space-time in the theory of relativity, and denied causality and determinism in quantum mechanics. The work of Einstein and Planck, that is, the development of relativity and quantum theory, is a major breakthrough in traditional physics theory and marks a major change in the direction of physics at the beginning of the 20th century. For a long time, we have been paying attention to the temple of physics supported by "classical mechanics" and "quantum mechanics", but we have not realized that these two pillars are closely maintained by physics in the19th century. /kloc-physics in the 0/9th century undoubtedly played an important role in the development and further improvement of classical mechanical systems and the emergence and rise of quantum mechanics and the concept of relative space-time.

Thanks to Professor Hahn, who led us to appreciate the development history of physics in the19th century, and also made me realize the unswerving scientific spirit deeply hidden in the hearts of scientific explorers.